1. Field of the Invention
This invention relates to the field of prostheses for the human knee.
2. Description of the Prior Art
During the use of the human knee there are many forces that act thereon, particularly during walking, running, or jumping. For example, in stepping down from a curb or jumping, the impact forces of the foot against the street or other surfaces are transmitted through the leg and the knee. Thus, these forces act on a knee prosthesis applying various forces, such as impact and tension forces, tending to cause the problem of loosening the prosthesis from the bone particularly over a period of time after the continual application of such forces. Also, for example, an impact or a compression force on one end of a prosthesis, i.e., either the anterior or the posterior end portion, would tend to cause a rocking of the prosthesis about its central portion and have the opposite effect on the other end. For example, an impact force acting on the anterior end of the prosthesis would tend to cause a tension pull-out force on the posterior end, and vice versa. In addition, there is the problem in prostheses with sharp edges on portions thereof to have a tendency to cut or crack the cement that has been provided to cement the prosthesis in place in the bone. Additionally, there are some other forces acting on the prosthesis, such as twisting forces, although these are minimal as compared with the impact and tension forces, and if a flat tibial plateau prosthesis is used it is of practically no consequence.
Heretofore, there have been various prostheses for use as the femoral component. Applicant has knowledge of a number of them, which have been patented. Some of these prior art devices are as follows: U.S. Pat. Nos. 3,852,830; 3,715,763; 3,728,742; and 3,774,244; German Pat. No. 939,226 and Italian Pat. No. 498,150. None of these patents disclose or suggest the improved prosthesis of the present invention.